Method of securing end contacts to cables

ABSTRACT

A method of providing end contacts on cable pieces which can be subjected to tensile load without damaging the core. To this end the end contact is slid on a collar which is provided on the cable piece and is mechanically connected thereto by means of shrinking the overlapping part.

Nov. 6, I973 United States Patent Geominy References Cited UNITED STATES PATENTS METHOD OF SECURING END CONTACTS TO CABLES FOREIGN PATENTS OR APPLICATIONS [75] Inventor: Louis Joseph Henri Geominy,

Edisonstraat, Venlo, Netherlands 1 Primary Examiner-Charles W. Lanham [22] Filed: Aug. 23, 1971 Assistant Examiner-James R. Duzan AttorneyFrank R. Trifari 1211 Appl. No.: 173,903

[57] ABSTRACT A method of providing end contacts on cable pieces [30] Foreign Application Priority Data Aug. 31, 1970 Netherlands.......................

which can be subjected to tensile load without damag- [52] U.S. 29/628, 29/629, 29/630 R, ing the core To this end the end Contact is slid on a 29/630 A H0lr 43/00 339/276 "r, 100 R- lar which is provided on the cable piece and is mechan- [51] Int.

ically connected thereto by means of shrinking the overlapping'part.

Field of Search 8 2 6 9 2 6 A O 3 6 9 2 m 5 3 Claims, 11 Drawing Figures PATENIEDunv 6197s 3.769.703 sum 1 c5 2 Fig. 5 V

- IN VENTOR.

LOUIS J.H. GEOMINY Agent METHOD OF SECURING END CONTACTS TO CABLES The invention relates to a method of securing end contacts to an electrical cable comprising a core provided with an electrical conductor and a fibre coating of an electrically insulating material. The core may consist of electrically conducting'material or of a support provided with an electrical conductor.

The invention is of special importance forcables whose fibre coating cannot easily be removed from the core for some reason or other without damaging this core.

An example of such a cable is a heating cable provided with a core of an electrically insulating material on which a heating wire is helically wound and which has a fibre coating. In such a cable additional problems occur in connection with the electrical contacting and the tensile load to which the cable is subjected during assembly and possible use. It must be avoided that such a tensile load gives rise to damage of the core.

End contacts for electrical cables are known which consist of a body provided with two aligned bores, the bore of small diameter being able to accommodate the electrical conductor and the bore of large diameter being able to accommodate the electrical conductor together with the electrically insulating envelope. After providing the end contact the cross-section of the end contact is locally reduced by means of tools suitable for this purpose in such a manner that the end-contact is clamped tightly tothe cable. A satisfactory securement is, however, only obtained when in case of tensile load thecore of the cable does not deform elastically and/or plastically in such a manner that it slides from out of the end contact. This manner of securing end contacts is therefore only suitable for cores consisting of a material which-is only deformed at heavy loads, for example, material consisting of a single or several steel wires. For cables including an easily deformable core or a flexible electrically insulating core on which an electrically conducting wire isvhelically wound, this manner of securement is therefore not very suitable.

An object of the present invention is, to provide a method of securing end contacts to cables of the abovementioned kind which may be sujected to tensile load.

diameter extends over the clamping piece and the folded coating up to beyond'the clamping piece, the cross-section of the end contact on the side of the clamping piece remote from the cable end being reduced.

The end contact is secured to the cable by means of the method according to the invention in such a manner that damage of the core is avoided in case of tensile load.

A preferred embodiment of the method according to theinvention is characterized in that the cross-section of the part of the end contact encompassing the core is at least locally reduced after it has been provided. 7

By using this measure, electrical contact between the end contact and the electrical conductor is ensured under all circumstances.

The reduction in cross-section according to this embodiment of the method may be effected simultaneously with the reduction of the cross-section of the part having the larger internal diameter.

The end contact which is used in the method accord- When the bore of small diameter extends up to the end of the end contact, a satisfactory electrical contact between the wall of this bore and the electrical conductor can also be obtained by driving a pin'or screw into the core through the aperture in the end contact after theend contact has been provided on the cable.

When the end contact is obtained by folding from ametal sheet it is recommended to use a pin or screw for this purpose, which is provided'with a bush sliding over the end contact when the pin or screw is driven in. As a result it is avoided that the end contact is deformed when the pin or screwis driven in. After the pin or screw is completely inserted, the bush. can be 7 connected to the end contact by means of welding, soldering, or by reducing thecross-section.

The clamping pieces or collars to be provided on the cable may consist of strip-shaped or wire-shaped material which is secured around the'cable with a clamping fit. The clamping pieces or collars may-consist of, for example,a metal bush or a wire or'foil wound on the cable in a single layer or in a spiral.

The method according to the invention is suitable for all kinds of cables comprising a corea'nd fibre coating and particularly for those cables in which a helically wound electrical conductor which extends throughout the length of the cable is present on a flexible core of electrically insulating material and in which the coating consists of fibres of electrically insulating material, for example, glass fibres. Cables of the latter construction mayhave sectors extending in the longitudinal direction of the cable which have mutually different temperatures during use: sectors which reach a high temperature during use may be alternated, for example, by Seetors whose temperature exceeds the ambiant temperature only to a slight extent during use. This effect may be brought about in various and mutually essentially different manners, namely ,by

A: winding the electrical conductor in the sectors which must not increase in temperature or may only increase in temperature to a slight extent during use ata greater pitch-than in the other sectors;

B: short-circuiting the windings of the electrical conductor in the sectors-which'must not increase in tem- .perature or may only'increase in temperature to a slight extent during use by means of electrically conducting metal strips extending in the longitudinal direction of the cable and being provided underneath or on the relevant winding while being brought in electrical contact therewith.

C: winding the electrical conductor in the sectors which must not increase in temperature or may only in'- crease in temperature to a slight extent during use in several layers with one on top of the other which layers are in mutually electrical contact.

The flexible core of electrically insulating material of such cables may consist of synthetic resin or a flexible inorganic material such as glass fibres or asbestos fibres.

The heating wire consists of a metal or alloy commonly used for this purpose. The outer coating consists of one or more braids and/or spinnings of, for example, glass fibre or a different fibre material.

In order that the invention may be readily carried into effect, some embodimentsthereof will now be described in detail by way of example with reference to the accompanying diagrammatic drawing in which:

FIGS. 1 to show different stages of the method according to the invention,

FIGS. 6 to 11 show different embodiments partly in side and front elevational views, partly in a crosssection of end contacts which are used in the method according to the invention.

In FIG. 1 a resistance heating cable 1 is shown in a side elevational view. The cable has a coating 2 partly removed in FIG. 1 consisting of a braid of glass fibres.

Furthermore, the cable has a core consisting of a sup-- port 3 likewise of glass fibres on which a heating wire 4 is wound helically. Two collars 5 and 6 of metal strip are clamped on the cable. Subsequently the cable is cut through in accordance with the broken line at A. One of the cable pieces then obtained is shown in FIG. 2. The glass fibre braid is loosened (7) on the part of the cable to the right of the collar 5 in FIG. 2. For the sake of clarity part of these loosened glass fibres is not shown. The glass fibres 7 are then folded back over the collar 5 (FIG. 3) and an end contact 8 of metal (for example, brass) is slid on the end of the cable. This end contact has two bores 9' and 10 which are aligned, the bore 9 being a blind bore. The diameter of the bores is'chosen preferably such that the support with the heating wire in bore 9 and the cable with collar 5 and folded glass fibres 7 are provided in bore 10 with a'running fit. FIG. 4 shows the end contact in a front elevational view. After the end contact 8 is slid on the cable end the cross-section of the bore 10 of large diameter is reduced at 11 on the side of the collar remote from the cable and next to the collar 5 by means of deformation tools s'uitable for this purpose. In order to bring about a satisfactory electrical contact between the electrical conductor 4 and the end contact 8 the cross-section .of the bore of small diameter is also reduced, for example,

FIG. 6 is a side elevational view andFI G. 7 is a crosssection of an embodiment of an end contact in which the part 13 accommodating the support with the heating wire has a rectangular cross-section. FIG. 8 shows a further embodimentin a cross-section and FIG.9 shows an embodiment in a front elevational view.

In the last-mentioned embodiment the bore 9 extends up to the end of the pin-shaped part 14. After this end contact is slid on the cable end, a pin as shown in FIG. 10 may be driven into the bore 9. If the end contact according to FIG. 8 is folded from a metal sheet it is recommended to use for this purpose a pin 15 provided with a cylinder 16 as is shown in a cross-section] 1. As a result the part 15 is prevented from opening. By providing the pins a satisfactory electrical contact between the electrical conductor and the part 14 of the end contact is obtained. Instead of using pins it is alternatively possible to use screws which are driven into the support.

The following advantages are obtained by using the method according to the invention. 7

By using a collar which is clamped on the cable, by folding back the fibre coating over this collar and by the manner of providing the end contact, the forces occurring in case of tensile load are compensated jointly by the core and the coating. As a result, the core and the coating cannot slide relative to each other in case of tensile load. When such a movement were to occur, the electrical conductor might break so that the cable would become unsuitable.

A further advantage is that no heat is developed within the part of the end contact encompassing the support with the electrical conductor, and as a result this part remains at a comparatively low temperature during use of the cable.

What is claimed is: I

1. A method of securing an end contact to an electrical cable having a core of electrically insulating material, an electrical conductor wound about said core and fibre coating of electrically insulating material covering said conductor, comprising the steps of securing a clamping collar about said fibre coating spaced from and near the end of said cable receiving said end contact, folding said fibre coating locatedbetween said collar and the end of said cable back over said collar and extending slightly therebeyond so that the conductor of said cable between said collar and the end of said cable is exposed, sliding an end contact having two aligned bores of different diameter onto the end of said cable so that said exposed conductor portion of said cable is received within the bore having the smaller diameter, said collar and folded fibre coating which extends slightly beyond the collar being accommodated within the larger of said bores, and reducing the crosss ection of said end contact at a point beyond said collar remote from the'end of the cable so as to secure said end contact to said cable by pressing saidfolded fibre coating against the unfolded fibre coating. 

1. A method of securing an end contact to an electrical cable having a core of electrically insulating material, an electrical conductor wound about said core and fibre coating of electrically insulating material covering said conductor, comprising the steps of securing a clamping collar about said fibre coating spaced from and near the end of said cable receiving said end contact, folding said fibre coating located between said collar and the end of said cable back over said collar and extending slightly therebeyond so that the conductor of said cable between said collar and the end of said cable is exposed, sliding an end contact having two aligned bores of different diameter onto the end of said cable so that said exposed conductor portion of said cable is received within the bore having the smaller diameter, said collar and folded fibre coating which extends slightly beyond the collar being accommodated within the larger of said bores, and reducing the cross-section of said end contact at a point beyond said collar remote from the end of the cable so as to secure said end contact to said cable by pressing said folded fibre coating against the unfolded fibre coating.
 2. The method according to claim 1 further comprising the additional step of reducing the cross section of that portion of the end contact accommodating said bared cable.
 3. A method according to claim 1 wherein the small bore of said end contact extends through said contact, and further comprising the additional step of driving a pin into the core of said cable after said end contact has been slid onto the end of said cable. 